Ambient Ion Mobility Spectrometry

While differential mobility analysis (DMA), field asymmetric waveform ion mobility spectrometry (FAIMS), and traditional embodiments of drift tube ion mobility spectrometry (DT-IMS) are capable of operation at atmospheric pressure, in current forms, each has limitations if considered for ambient analysis of droplets and solvated ions. In this case, ambient means droplets and ions in a stable equilibrium with their environment, that is, no significant evaporation or ongoing desolvation. The analysis of droplets and ions in this state is of critical importance in understanding the factors contributing to accelerated reactions and general ion formation occurring within an electrospray plume. Tandem DMA is the most obvious method of performing such analysis as this has previously been demonstrated for studies on aerosol growth and nucleation [9, 10]. DMA measurements have even been used to study the ion evaporation model (IEM) within electro- sprayed droplets <3 nm [11, 12]; however these studies are limited by the range of the DMA which must be designed for measurements within specific particle sizes. Additionally, tandem DMA instruments in particular are instrumentally complex in nature, require precise control of gas flow, and the fundamentals of aerosol transfer within and between individual DMAs must be well understood to interpret the results of such experiments.

The disposability and cost-effectiveness of instruments employing 3D printed components makes them amenable to use in harsh environments such solvent-saturated gas environments necessary to halt the evaporation of droplets. Through extensions of the work presented in this dissertation it is hoped that new, relatively low cost, and modular instrumentation will be developed to allow for analysis of solvated clusters and nanometer size droplets to be measured in a rapid and ambient manner. From these measurements it may be possible to gain a better understanding of reaction acceleration within electrosprayed droplets.

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